Monitoring of Decontamination
Methods
Biological and chemical indicators are used to monitor the lethality of
a sterilization process and ensure the effectiveness of sterilization.
They are also used to routinely monitor a sterilizer’s performance
according to practices developed and published by the “Association for
the Advancement of Medical Instrumentation” (AAMI), the “Association
for peri-Operative Registered Nurses” (AORN) and the “Centers for
Disease Control” (CDC).
Biological indicators (BI) contain large number of highly resistant
spores of Geobacillus stearothermophilus . Destroying and killing
of these spores in the BI by the tested sterilization processes implies
that the sterilization process is effective enough to kill other
potential pathogens. BIs are commercially available as test kits, and
they are used to assess the sterility level of water, food containers,
and medical and surgical tools and instruments in hospital rooms. When
the test kit is incubated, the spores of G.Stearothermophilusgerminate in the kit and produce α-glucosidase enzymes that react with
the fluorescent media (4-methyl-umbelliferyl-α-D-glucopyranoside) in the
kit and produces a fluorescent signal, which is then detected by the
detector in the incubator. The advantage of BIs is that they are quite
quick tests, only requiring 20 minutes for both incubation and detection
([BSI], 2014a; ANS, 2017; Gordon, 2013; Swenson, 2012).
In contrast to BIs, chemical indicators (CIs) do not contain resistant
spores, and instead use special chemicals or pigments that change
physical properties or color when specific environmental conditions have
been attained. As such, they are able to monitor decontamination methods
based on the fulfillment of one or more of the parameters required for a
satisfactory sterilization process. This physical or chemical change is
interpreted as a pass or fail result. For example, when using steam for
sterilization such as in an autoclave, a solid CI that converts to
liquid upon exposure to steam can be used to confirm the quality of
sterilization. When pigments are used, they chemically react with some
critical parameters of the sterilization process and consequently the
color changes to its endpoint color, indicating that the parameters for
sterilization have been met. ([BSI], 2001, 2014b; ANS, 2017).